| 3d Transition metal coordination cluster has broad application prospects in light,electricity,magnetism,catalysis and other fields due to their diverse structural characteristics,and become a hot spot and foreword in the field of modern research.Therefore,directional design,controllable synthesis and performance regulation of coordination clusters have become the goal people have been pursuing and the assembly process and mechanism research is the basis for the real realization of controlled synthesis.To advance the study of self-assembly by setting the foundation for the rational construction of coordination clusters with targeted connection,shape,and properties,a better understanding of their mechanism of formation involved is highly desired.However,due to the complex and changeable reaction conditions,the coexistence of various intermediates and the change of species abundance with time,it is very difficult to study the process assembly and mechanism of metal clusters.At present,mass spectrometry has become a powerful characterization method,which can directly detect liquid samples under mild conditions and achieve rapid detection of complex species in solution.In this paper,the reaction of Ni L2or(1-methyl-1H-benzo[d]imidazol-2-yl)methanethiol with MII(H2O)6(NO3)2(M=Co,Ni,Zn)has been successfully constructed a series of adjacent heterometallic or molecular clusters.Based on the good accumulation of our group on the assembly process and mechanism of coordination clusters,the basic solid solution properties and assembly process of these compounds were studied by tandem crystallographic and mass spectrometric techniques.The full text is divided into three chapters:The first chapter is the introduction to introduce the research progress and challenges in the assembly process of multinuclear metal clusters;the development and application of electrospray ionization mass spectrometry(ESI-MS)in the assembly process of coordination cages,polyoxometalates,high nuclear nanoclusters and coordination molecular clusters;the new ideas and strategies for studying the formation process and mechanism of clusters by ESI-MS;Finally,we elaborated the significance and research content of this paper.Chapter 2 describes that the original work done in the presence of Et3N basic condition the reaction of[Ni(L1)2](L1=2-ethoxy-6-(N-methyl-iminomethyl)phenolate)with Ni II(H2O)6(Cl O4)2leads to[Ni7(?3-OH)6(L1)6]2+,where the application of ESI-MS of the reaction solutions as function of time revealed the following stepwise assembly process,Ni(L1)2?[Ni2(L1)3]+?[Ni4(OH)2(L1)4]2+?[Ni7(OH)6(L1)6]2+.What was not clear in this study was the importance of the base and the counter-anion of the metal salt.In this manuscript we explore the reaction without base.The results were quite unexpected.In contrast,its reaction with MII(H2O)6(NO3)2in the absence of base leads to two crystallographic structural types[M3II(L1)4(NO3)2(H2O)2]·CH3CN for M=Ni(1)or Co(4,x=0–3)and[MIINi 2II(L1)4(NO3)2]for M=Zn(2)or Co(3).Herein,we present the results of SCXRD,TGA,IR,ESI-MS and magnetism.Interestingly,three slightly different formation processes have been identified using ESI-MS as follows:for 1–{Ni(L1)2?[Ni2(L1)(NO3)2]+?[Ni2(L1)2(NO3)]+?[Ni2(L1)3]+?[Ni3(L1)4(NO3)]+};for 2–{Ni(L1)2?[Zn Ni(L1)2(NO3)]+?[Zn Ni2(L1)4(NO3)]+};for 3 and 4–{Ni(L1)2?[CoxNi2-x(L1)2(NO3)]+?[CoxNi2-x(L1)3]+?[CoxNi3-x(L1)4(NO3)]+}.The presence of base provides the strong hydroxide ligand to bridge the metals into the very stable edge-sharing Brucite net[Ni7(OH)6(L1)6]whereas without the base there is an interplay between the weak coordinating nitrate and water stabilizing the two structural types via the different formation processes.In addition,two tetranuclear heterometallic clusters with different configurations were obtained by adding sodium azide into the reaction of Ni L2with Co(H2O)6(NO3)2,namely compound 5{[CoxNi4-x(L1)4(N3)4]}and 6{[Na2Co2(L1)4(N3)4]}.The single crystal mass spectrometry data of compound 5 show that the strongest peak is[Na M(L1)2]+(m/z=437.10)which is unstable and short-term crystallization.As the reaction proceeds,compound 5 dissolves gradually and assembles step by step with Co2+,Na+,N3-in solution to form 6,which the possible assemble process[Na M(L1)2]+?[Co2(L1)4]+?[Na Co2(L1)4(N3)]+?[Na2Co2(L1)4(N3)2]+.In chapter 3,we synthesized a series of Zn/Ni-based clusters by the reaction of(1-methyl-1H-benzo[d]imidazol-2-yl)methanethiol ligand(HL2)with Zn(NO3)2·6H2O/Ni(NO3)2·6H2O under acidic environment and at different temperatures.Some interesting phenomena were found,such as S-S coupling at room temperature,C-S fracture at 140°C,in-situ reaction with nitrate at 120°C,etc.ESI-MS reveal the process of self-assembly driven by coordination clusters of different temperature solvent hot black box reaction and in-situ transformation of ligands.The solvothermal reactions at different temperatures and driven self-assembly coordination clusters with in situ transformation of ligands was revealed by ESI-MS.Firstly,mononuclear zinc cluster[Zn(L3)Cl3](7)was synthesized by the reaction of ligand with Zn(NO3)2·6H2O at room temperature.HL3was the ligand after S-S coupling of ligand HL2,and fortunately,we obtained the single crystal structure of HL3.A linear trinuclear cluster[Zn3(L2)4(NO3)2](8)was obtained at 80°C,and we can infer the progressive degradation process by different in-source energies mass spectrometry:[Zn3(L2)4(NO3)]+?[Zn2(L2)3]+?[Zn2(L2)2(NO3)]+?[Zn(L2)]+.One-dimensional chain polymer[Zn5(L')4(OCH3)2(SO4)]n(9)was obtained at 120°C.During the refined the crystal structure,we found the in-situ reaction of ligand and nitrate.And the in-situ ligand(H2L')was obtained by acidolysis and recrystallization of the polymer with concentrated hydrochloric acid.The single crystal mass spectrometry showed that 9 is stable under the ionization conditions and found that the framework fragment of[Zn5(L')4]2+,dimer[Zn10(L')8(SO4)]2+and trimer[Zn15(L')12(SO4)2]2+.Compound 10 with tetrahedral coordination between ligand(L')and zinc ion in the form of Zn N2Cl2was obtained at140°C.It was found that mainly hydrogen bond of 10 is H···Cl by the hirshfeld surface and fingerprint plot.In addition,the umbrella-like trinuclear cluster{[Ni3(L2)3S(NO3)]}(11)was obtained when the using Ni(H2O)6(NO3)2instead of Zn(H2O)6(NO3)2.The pressure mass spectrometry showed that compound 11 is stable under the ionization conditions.In this research,a series of clusters with different nuclei were obtained by changing the reaction temperature,which proved that the temperature had a very important influence on the design and synthesis of clusters. |
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